Gas chromatography is a central analytical technology having a large variety of applications in a broad range of fields, especially when used in association with mass spectrometry for improved sensitivity, selectivity and sample identification capability. However, while gas chromatography (GC) is a powerful analytical tool, GC analysis requires long analysis times, typically in the order of 30-60 min when operated with standard gas chromatography columns (typically 30 m) combined with standard GC ovens with their slow temperature programming rate and slow cooling down for being ready to next analysis.
In view of the long time associated with standard GC analysis, several fast GC systems have been developed that incorporate low thermal mass devices that provide fast temperature programmable heating and cooling rates for the GC separation columns.
Relevant and related to this application is US 2012-0085148, which discloses a low thermal mass fast GC, based on the transfer of a gas chromatography column through a gas chromatograph oven as a flexible non-rigid capillary into a resistively heated metal tube having opposing input and output ends. The input and output ends of the resistively heated metal tube are located near a hole in the gas chromatograph oven body so that a substantial portion of the column in the heated metal tube is located outside the gas chromatograph oven and so that the input and output ends project a short distance inside the gas chromatograph oven. The capillary column is connected in the gas chromatograph oven as a flexible capillary with both the gas chromatograph injector and detector. Both ends of the resistively heated metal tube are connected to a power supply that resistively heats the heated metal tube in a time programmed manner to facilitate fast temperature program of the capillary column.
An important feature of the fast gas chromatograph according to US 2012-0085148 is that the capillary column and the resistively heated metal tube are configured such that transferring the capillary column through the gas chromatograph oven into the resistively heated metal tube and introducing the capillary column from the heated metal tube into the gas chromatograph oven is reversible, without removal of the resistively heated metal tube. However, the fast gas chromatograph disclosed in this reference is still subject to a few limitations including the following:    1. Friction in column insertion. The process of column insertion into the heated metal tube is involved with friction that increases as the heated metal tube length is increased, particularly if the internal diameter of the heated metal tube is not much larger than the outer diameter of the GC capillary column as is desirable for minimizing the heated tube thermal mass. This friction is largely increased due to the curving and coiling of the heated metal tube to diameters such as 12-15 cm in order to have small fast GC house dimension. It can also emerge and increase from imperfect coiling. As a result of this friction and in order to enable safe in-field column replacement by the fast GC users, the heated metal tube length and with it the capillary column length is restricted to typically 2 m such that fast GC separation is impeded.    2. Possible capillary column breakage. The insertion of the fused silica gas chromatography capillary columns into the narrow resistively heated metal tube is a delicate process that could lead into the breakage of the fused silica capillary column inside the metal heating tube with difficulties to remove the broken capillary pieces. GC capillary columns are delicate as their brittle fused silica tube thickness is only about 40μ and although they are supported by Vespel plastic they are still delicate. Furthermore, the heated metal tube often includes some imperfections that can scratch the thin protective Vespel layer and lead this way to column breakage.    3. Fixed small heated metal tube and capillary column length. The resistively heated metal tube is heated and operated with a power supply. The heated tube temperature depends on the heating current (power per unit length) while its operational voltage linearly increases with the tube length and with it the total power requirements from the power supply as well as the power supply size, weight and cost, and similarly the size and cost of the related cooling fans. Furthermore, higher voltage is also not as safe. Thus, for practical electrical power saving reasons the length of the heated tube metal is restricted. The heated metal tube length restriction also emerges from the growing friction with its length and with it the danger to the column integrity during its insertion into the heating metal tube. Consequently the length of the fused silica capillary column is restricted and its separation capability is limited due to its limited length. Even if the power supply could provide any needed voltage, once the heated metal tube length is provides in a given length, the GC capillary column length is fixed and cannot be changed which reduces the fast GC flexibility in trade-off of separation and speed of analysis.Thus, it is desirable to improve the fast GC according to US 2012-0085148 by reducing friction between the capillary column and its heated metal tube oven during the capillary column insertion or removal for its replacement. Reducing friction will reduce the chances of column breakage during its insertion. Furthermore, it is also important to enable freedom in the selection of capillary column length while complying with the length limitation of the heated metal tube. These challenges are addressed in novel and unexpected ways by the present invention.